PRO0812-Lentils and reduction of arsenic toxicity
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PRO0812
Can arsenic toxicity in mammals be reduced by feeding Saskatchewan grown lentils?
INVESTIGATORS
Principal Investigator: Dr. Judit Smits, University of Saskatchewan
Co-Investigator(s):
Dr. Josef Hormes Canadian Light Source, UofS
Dr. Albert Vandenberg, University of Saskatchewan
Dr Regina Krohn, University of Calgary
Dr. Gerald Combs, USDA, Grand Forks Human Nutrition Research Centre
McGill Collaborator:
Dr. Koren Mann
STUDY SPONSORS
National Sciences and Engineering Research Council of Canada (NSERC)
Saskatchewan Pulse Growers
TYPE OF STUDY
Health Outcome: Pre-clinical trial: Mammalian model feeding trial
OBJECTIVES
1. To design and validate a mammalian model of arsenic toxicity and determine the most
sensitive bioindicators (e.g., measurable biochemical, hormonal, immunological,
pathological responses) of adverse health effects from this exposure.
2. To feed laboratory rodents exposed to environmentally meaningful levels of arsenic, with
high and low selenium rodent diets to determine if dietary selenium can reduce damage
induced by arsenic exposure.
3. In the same experimental model, to feed animals nutritionally balanced diets made from
lentils with only selenium levels being different (because the lentils were grown in SK and
Western USA), and measure differences in arsenic induced damage.
4. To test the potential of high-selenium lentils from the Canadian prairies as a therapeutic
food to alter the outcome of arsenic-stimulated atherosclerosis (plaque development
within blood vessels) using a mouse model.
PRO0812-Lentils and reduction of arsenic toxicity
WHY STUDY NEEDED
Chronic arsenic (As) toxicity (arsenicosis) causes serious health problems in humans
including disfiguring skin lesions, common cancers, and severe artherosclerosis. Selenium
(Se) is a micronutrient thought to play an important role in mitigating the health costs
associated with arsenic toxicity. Clinical results from trials in which people have been
supplemented with Se have shown increased longevity and remarkable decreases in
incidence of common cancers. Selenium is an antagonist of As toxicity and has been shown
to decrease As concentrations in blood and hair and to be protective against genetic damage
from As toxicity in laboratory rodents.
It has been proposed that Se, supplemented in tablet form to children and adults, would have
a beneficial effect on wide spread pandemic arsenic toxicity in South Asia and, although
there is growing evidence to support this hypothesis, definitive proof is lacking. Such proof
would entail a controlled study in which As exposed animals are treated with low Se diets, or
the same diets except for supplemental Se treatment, which can both be compared with
nutritionally similar diets, except that Se is naturally incorporated into the food base of the
diet (i.e., SK lentil).
Current research shows that Saskatchewan grown lentils are a uniquely rich source of Se
due to the selenium rich soils in the province. Thus lentils from Saskatchewan present a
unique opportunity for natural Se biofortification and could provide a whole food solution to
arsenic toxicity.
The aim of the study was to examine the potential benefits of selenium-rich lentils grown in
Saskatchewan in counteracting arsenic toxicity.
HYPOTHESIS
Increased dietary selenium will reduce the body burdens of arsenic and decrease clinical
signs of chronic arsenic toxicity.
STUDY DESIGN
In four separate experimental studies, laboratory rodents were used to investigate the effects
of chronic arsenic poisoning and the potential of diets made from high selenium lentils to
reduce or eliminate the damage caused by arsenic.
Study 1: Dose-dependent study
Established the dose-dependent effects of As using 3 environmentally relevant levels of arsenic
(0.4, 4, and 40 ppm) by exposing rats to arsenic in their drinking water for 18 weeks.
Study 2: Compared effects of consuming high, versus low Se, otherwise nutritionally
matched, rodent chow to reduce arsenic toxicity. Rats received As (40 and 80 ppm) in
drinking water and challenge diets with three levels of Se (deficient: 50.01 ppm, adequate:
0.15 ppm, and fortified: 0.6 ppm) for 16 weeks.
Study 3: Compared effects of consuming diets made from high-Se SK lentils versus low-Se
lentils from NW United States to reduce arsenic toxicity. Rats drank control (0 ppm As) or As
(40 ppm) water while consuming SK lentils (0.3 ppm Se) or NW USA lentils (0.01 ppm Se)
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PRO0812-Lentils and reduction of arsenic toxicity
diets for 14 weeks.
Study 4: Performing a study on ApoE-/- mice with our collaborators at McGill University,
Montreal. Mice were exposed to 200 ppb As in their drinking water while being fed a high- or
low-selenium lentil diet. After 13 weeks the atherosclerosis lesion area and plaque
composition were assessed, and lipid and glutathione (GSH) concentrations in plasma
measured.
In general, animals were exposed for 3+ or 4 months to the arsenic water and respective
diets. Food and water consumption, growth rate and behavior were assessed every 1 to 2
days. Samples (blood, urine, feces) were collected to examine biological / health responses
in the experimental animals on a monthly basis. When animals were humanely euthanized at
the end of each of the studies, detailed necropsies (autopsies) were conducted. Gross and
histopathology examination of major organs (liver, lung, kidney, spleen, thyroid glands, lungs,
heart, blood vessels in extremities) was carried out. Tissue samples (liver and blood) and
excreta (urine and feces) were analyzed to determine responses to the selenium treatments.
All the studies and the animals used were carried out under the auspices and with approved
experimental protocols from the Canadian Council on Animal Care and University of Calgary
or University of Saskatchewan Animal Care Committees.
The diets were all nutritionally balanced and formulated by Harlan Laboratories, a
commercial rodent diet manufacturer. Only the selenium levels were different. Lentils for all
the diets were supplied by Dr A. Vandenberg, University of Saskatchewan. The same types
of lentil were used, but they had been grown in regions with high (Saskatchewan) or low
(Idaho) selenium soil, which is reflected in lentils grown on those soils.
FINDINGS
Arsenic–exposed animals on high selenium diets compared to those on selenium deficient
diets showed the following:
 Higher blood stores of the major, protective antioxidant, glutathione (GSH)
 Decreased liver damage as measured by oxidative damage in liver tissue (TBARS
assay)
 Recovery of the antibody mediated immune response which is suppressed by arsenic
exposure
 High Se lentil diets, and body burdens of As were reduced, as was evident through
lower arsenic residues in the kidneys, and higher fecal and urinary arsenic excretion
in animals on the high selenium diets.
 Arsenic-exacerbated plaque formation was reduced or completely abolished in
specific areas of the aorta of mice on the Se-fortified lentil diet, whereas vascular
plaques were increased in As-exposed mice on the Se-deficient and -adequate diets.
Additionally, Se deficiency contributed to pro-atherogenic composition of serum lipids
in As-exposed mice as indicated by HDL:LDL. This study was the first to show the
potential of high-Se lentils to protect against As-triggered atherosclerosis
SIGNIFICANCE OF STUDY
In a rodent model, the key achievements of this study were the following:
1. Determined the dose-dependent health effects of arsenic (As) exposure in a rodent
model
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PRO0812-Lentils and reduction of arsenic toxicity
2. Showed it was possible to reverse these health effects with commercial diets fortified with
selenium.
3. Showed that selenium-rich Saskatchewan grown lentils diets also increased arsenic
detoxification from the body and decrease damage from As exposure.
4. Through using a mouse model of atherosclerosis, we showed that high Se lentil diets
reduced the plaque formation in the aorta and improved the blood cholesterol profile in
favour of higher beneficial High Density Lipoproteins compared with the detrimental Low
Density Liporoteins.
PUBLICATIONS, PRESENTATIONS,
EDUCATIONAL MATERIALS PRODUCED
1. Krohn RM., M Lemaire, Negro Silva LF, Mann KK, Smits JEG. August 2015. Highselenium lentil diet protects against arsenic-induced atherosclerosis in a mouse model. In
Press -Journal of Nutritional Biochemistry
2. Sah S., A. Vandenberg, J.E. Smits. 2013. Treating chronic arsenic toxicity with high
selenium lentil diets. Toxicology and Applied Pharmacology 272: 256-262 doi:
10.1016/j.taap.2013.06.008
3. Sah S., Judit E. G Smits. 2012. Dietary selenium fortification: A potential solution to
chronic arsenic toxicity. Toxicology & Environmental Chemistry 94(7): 1453-1465
DOI:10.1080/02772248.2012.701104
4. Nain S., Smits, J.E.G. 2012. Pathological, immunological and biochemical biomarkers of
sub-chronic arsenic toxicity in experimental rats. Environmental Toxicology 27(4): 244–
254
VALUE TO PRODUCERS/PULSE INDUSTRY
Increased imports of high selenium lentils from Canada may provide a whole food solution to
the people affected with arsenicosis in severely affected countries (Bangladesh, northeastern
India and the IndoGangetic plains region).
High selenium lentils may confer cardiovascular health benefits to other mammals, including
humans, based on findings in experimental animals, but this requires further research.
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